add notification message and publish to mediatr

mediatr.go

@@ -2,20 +2,26 @@ package mediatr
 
 import (
 	"context"
-	"github.com/pkg/errors"
 	"reflect"
+
+	"github.com/pkg/errors"
 )
 
 type RequestHandler[TRequest any, TResponse any] interface {
 	Handle(ctx context.Context, request TRequest) (TResponse, error)
 }
 
+type NotificationHandler[TNotification any] interface {
+	Handle(ctx context.Context, notification TNotification) error
+}
+
 var requestHandlersRegistrations = map[reflect.Type]interface{}{}
+var notificationHandlersRegistrations = map[reflect.Type][]interface{}{}
 
 type Unit struct{}
 
 // RegisterRequestHandler register the request handler to mediatr registry.
-func RegisterRequestHandler[TRequest any, TResponse any](h RequestHandler[TRequest, TResponse]) error {
+func RegisterRequestHandler[TRequest any, TResponse any](handler RequestHandler[TRequest, TResponse]) error {
 	var request TRequest
 	requestType := reflect.TypeOf(request)
 
@@ -25,7 +31,7 @@ func RegisterRequestHandler[TRequest any, TResponse any](h RequestHandler[TReque
 		return errors.Errorf("registered handler already exists in the registry for message %s", requestType.String())
 	}
 
-	requestHandlersRegistrations[requestType] = h
+	requestHandlersRegistrations[requestType] = handler
 
 	return nil
 }
@@ -35,7 +41,39 @@ func RegisterRequestBehavior(b interface{}) error {
 	return nil
 }
 
-// Send the request to its corresponding handler.
+// RegisterNotificationHandler register the notification handler to mediatr registry.
+func RegisterNotificationHandler[TEvent any](handler NotificationHandler[TEvent]) error {
+	var event TEvent
+	eventType := reflect.TypeOf(event)
+
+	handlers, exist := notificationHandlersRegistrations[eventType]
+	if exist == false {
+		notificationHandlersRegistrations[eventType] = []interface{}{handler}
+		return nil
+	}
+
+	notificationHandlersRegistrations[eventType] = append(handlers, handler)
+
+	return nil
+}
+
+// RegisterNotificationHandlers register the notification handlers to mediatr registry.
+func RegisterNotificationHandlers[TEvent any](handlers ...NotificationHandler[TEvent]) error {
+	if len(handlers) == 0 {
+		return errors.New("no handlers provided")
+	}
+
+	for _, handler := range handlers {
+		err := RegisterNotificationHandler[TEvent](handler)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// Send the request to its corresponding request handler.
 func Send[TRequest any, TResponse any](ctx context.Context, request TRequest) (TResponse, error) {
 
 	requestType := reflect.TypeOf(request)
@@ -57,3 +95,27 @@ func Send[TRequest any, TResponse any](ctx context.Context, request TRequest) (T
 
 	return response, nil
 }
+
+// Publish the notification event to its corresponding notification handler.
+func Publish[TNotification any](ctx context.Context, notification TNotification) error {
+	eventType := reflect.TypeOf(notification)
+
+	handlers, ok := notificationHandlersRegistrations[eventType]
+	if !ok {
+		return errors.Errorf("no handlers for notification %T", notification)
+	}
+
+	for _, handler := range handlers {
+		handlerValue, ok := handler.(NotificationHandler[TNotification])
+		if !ok {
+			return errors.Errorf("handler for notification %T is not a Handler", notification)
+		}
+
+		err := handlerValue.Handle(ctx, notification)
+		if err != nil {
+			return errors.Wrap(err, "error handling notification")
+		}
+	}
+
+	return nil
+}

mediatr_benchmarks_test.go

@@ -0,0 +1,48 @@
+package mediatr
+
+import (
+	"context"
+	"reflect"
+	"testing"
+)
+
+func Benchmark_Send(b *testing.B) {
+	// because benchmark method will run multiple times, we need to reset the request handler registry before each run.
+	requestHandlersRegistrations = make(map[reflect.Type]interface{})
+
+	handler := &RequestTestHandler{}
+	errRegister := RegisterRequestHandler[*RequestTest, *ResponseTest](handler)
+	if errRegister != nil {
+		b.Error(errRegister)
+	}
+
+	b.ResetTimer()
+	ctx := context.Background()
+	for i := 0; i < b.N; i++ {
+		_, err := Send[*RequestTest, *ResponseTest](ctx, &RequestTest{Data: "test"})
+		if err != nil {
+			b.Error(err)
+		}
+	}
+}
+
+func Benchmark_Publish(b *testing.B) {
+	// because benchmark method will run multiple times, we need to reset the notification handlers registry before each run.
+	notificationHandlersRegistrations = make(map[reflect.Type][]interface{})
+
+	handler := &NotificationTestHandler{}
+	handler2 := &NotificationTestHandler4{}
+
+	errRegister := RegisterNotificationHandlers[*NotificationTest](handler, handler2)
+	if errRegister != nil {
+		b.Error(errRegister)
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		err := Publish[*NotificationTest](context.Background(), &NotificationTest{Data: "test"})
+		if err != nil {
+			b.Error(err)
+		}
+	}
+}

mediatr_test.go

@@ -38,20 +38,76 @@ func Test_Send_Should_Throw_Error_If_No_Handler_Registered(t *testing.T) {
 func Test_Send_Should_Return_Error_If_Handler_Returns_Error(t *testing.T) {
 	expectedErr := "error handling request"
 	handler3 := &RequestTestHandler3{}
-	_ = RegisterRequestHandler[*RequestTest2, *ResponseTest2](handler3)
+	errRegister := RegisterRequestHandler[*RequestTest2, *ResponseTest2](handler3)
+	if errRegister != nil {
+		t.Error(errRegister)
+	}
 	_, err := Send[*RequestTest2, *ResponseTest2](context.Background(), &RequestTest2{Data: "test"})
 	assert.Containsf(t, err.Error(), expectedErr, "expected error containing %q, got %s", expectedErr, err)
 }
 
-func Test_Send_Should_Return_Response_If_Handler_Returns_Success(t *testing.T) {
+func Test_Send_Should_Dispatch_Request_To_Handler_And_Get_Response(t *testing.T) {
 	handler := &RequestTestHandler{}
-	_ = RegisterRequestHandler[*RequestTest, *ResponseTest](handler)
+	errRegister := RegisterRequestHandler[*RequestTest, *ResponseTest](handler)
+	if errRegister != nil {
+		t.Error(errRegister)
+	}
 	response, err := Send[*RequestTest, *ResponseTest](context.Background(), &RequestTest{Data: "test"})
 	assert.Nil(t, err)
 	assert.IsType(t, &ResponseTest{}, response)
 	assert.Equal(t, "test", response.Data)
 }
 
+func Test_RegisterNotificationHandler_Should_Register_Multiple_Handler_For_Notification(t *testing.T) {
+	handler1 := &NotificationTestHandler{}
+	handler2 := &NotificationTestHandler{}
+	err1 := RegisterNotificationHandler[*NotificationTest](handler1)
+	err2 := RegisterNotificationHandler[*NotificationTest](handler2)
+
+	assert.Nil(t, err1)
+	assert.Nil(t, err2)
+}
+
+func Test_RegisterNotificationHandlers_Should_Register_Multiple_Handler_For_Notification(t *testing.T) {
+	handler1 := &NotificationTestHandler{}
+	handler2 := &NotificationTestHandler{}
+	handler3 := &NotificationTestHandler4{}
+	err := RegisterNotificationHandlers[*NotificationTest](handler1, handler2, handler3)
+
+	assert.Nil(t, err)
+}
+
+func Test_Publish_Should_Throw_Error_If_No_Handler_Registered(t *testing.T) {
+	expectedErr := fmt.Sprintf("no handlers for notification %T", &NotificationTest{})
+	err := Publish[*NotificationTest](context.Background(), &NotificationTest{})
+	assert.Containsf(t, err.Error(), expectedErr, "expected error containing %q, got %s", expectedErr, err)
+}
+
+func Test_Publish_Should_Return_Error_If_Handler_Returns_Error(t *testing.T) {
+	expectedErr := "error handling notification"
+	handler1 := &NotificationTestHandler{}
+	handler2 := &NotificationTestHandler{}
+	handler3 := &NotificationTestHandler3{}
+
+	errRegister := RegisterNotificationHandlers[*NotificationTest](handler1, handler2, handler3)
+	if errRegister != nil {
+		t.Error(errRegister)
+	}
+	err := Publish[*NotificationTest](context.Background(), &NotificationTest{})
+	assert.Containsf(t, err.Error(), expectedErr, "expected error containing %q, got %s", expectedErr, err)
+}
+
+func Test_Publish_Should_Dispatch_Notification_To_All_Handlers_Without_Any_Response_And_Error(t *testing.T) {
+	handler1 := &NotificationTestHandler{}
+	handler2 := &NotificationTestHandler4{}
+	errRegister := RegisterNotificationHandlers[*NotificationTest](handler1, handler2)
+	if errRegister != nil {
+		t.Error(errRegister)
+	}
+	err := Publish[*NotificationTest](context.Background(), &NotificationTest{})
+	assert.Nil(t, err)
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////////
 type RequestTest struct {
 	Data string
@@ -91,3 +147,44 @@ type RequestTestHandler3 struct {
 func (c *RequestTestHandler3) Handle(ctx context.Context, request *RequestTest2) (*ResponseTest2, error) {
 	return nil, errors.New("some error")
 }
+
+///////////////////////////////////////////////////////////////////////////////////////////////
+type NotificationTest struct {
+	Data string
+}
+
+type NotificationTestHandler struct {
+}
+
+func (c *NotificationTestHandler) Handle(ctx context.Context, notification *NotificationTest) error {
+	return nil
+}
+
+///////////////////////////////////////////////////////////////////////////////////////////////
+type NotificationTest2 struct {
+	Data string
+}
+
+type NotificationTestHandler2 struct {
+}
+
+func (c *NotificationTestHandler2) Handle(ctx context.Context, notification *NotificationTest2) error {
+	return nil
+}
+
+///////////////////////////////////////////////////////////////////////////////////////////////
+
+type NotificationTestHandler3 struct {
+}
+
+func (c *NotificationTestHandler3) Handle(ctx context.Context, notification *NotificationTest) error {
+	return errors.New("some error")
+}
+
+///////////////////////////////////////////////////////////////////////////////////////////////
+type NotificationTestHandler4 struct {
+}
+
+func (c *NotificationTestHandler4) Handle(ctx context.Context, notification *NotificationTest) error {
+	return nil
+}